I can't really put an exact number on it, seeing how the product isn't mine nor is there a common frame of reference. On the conservative side, it'll take at least twice as long, likely longer, as opposed to keeping the bud in a container with air. There's really only one reason to suck-out most of the air and it's to preserve the product (ie. slow down its decomposition). The risk of mold is essentially nonexistent, if the flowers are at the curing stage. Good luck.
How would do you take measurements? Do you take out the bud to feel how wet or dry it is? So would two times a day work? when I wake up and when I call it a night?